Link aggregation (LA), which is known as a technique for using a plurality of physical lines as a single logical line, is standardized as IEEE 802.3ad. With LA, even if a failure occurs in one of the physical lines, communication may be continued with the remaining physical lines. Communication quality is therefore improved compared to communication where only a single physical line is used. In addition, with LA, because a plurality of physical lines is used as a single logical line, the bandwidth of all the physical lines may be used as the bandwidth of the logical line. Bandwidth may be therefore increased without using high-speed physical lines.
One example of a technique using LA include a technique that uses a hash function to determine one of a plurality of physical lines to be used in order to distribute traffic over the plurality of physical lines. Another example is a technique that assigns priority levels to connections between nodes, where the connections use LA, and when changing transmission paths selects one of the connections that has a low priority level in order to suppress the accompanying reduction in throughput when changing transmission paths.
Examples of related art include Japanese Laid-open Patent Publication Nos. 2006-115392 and 2006-5437.